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<title>Query Hints</title>
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<p>
Query hints are specified at the SPARQL layer using magic predicates.  A few
special query hints are interpreted by the parser itself (currently only the
QueryID).  Most query hints are handled by the {@link ASTQueryHintOptimizer}.
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<p>
Query hints wind up being handled in several different ways.  Some of them
cause query wide attributes to be set on the AST2BOpContext.  Other query hints
are transferred into ASTBase annotations and then subsequently intepreted either
by other IASTOptimizers or by AST2BOpUtility.  Finally, some query hints are
set on the "queryHints" property of the ASTBase nodes.  Those query hints are
then transferred onto PipelineOps as they are generated.
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